Morning journal and courier., 1887-05-18
OTHER WORLDS THAN OURs.


 Why Planetary Life Varies With the
 Size of the Planet.
 IRichard A. Proctor in the St. Louis Globe Demo-
 crat.
 May we not-nay, rather must we not admit that among the planets within the so- lar system varieties ot actual nature must ex- ist? Is it antecedently likely that the stages of the life of giant planet like Jupiter will resemble in detail those of planet like our earth-having but ,340th of that giants masss And on the other hand, it is reasona- ply probable that the stages of our earth's life will resemble those of the moon, which she exceeds in mass more than eighty timess The giant planet, the terrestrial planet the small planet, may all three pass through the same general stages of life. Each may have it's glowing vaporous stage, it's fiery stage, it's middle life, when clothed with air and water it is fit to be the abode of living creatures, it's old age and finally it's stage Cf decrepi- tude and death; much the elephant, the man and the mouse (nay, the land animal, the bird, the fish, the insect and the mollusk, the animal and the vegetable) nave each their infancy, their youth, their middle life, their old age and their death. But precisely as the details of the life development of ele- phant, man and mouse are unlike, while those of the life development of other crea- lures differ inter still more, so 1t is probable that the features of planets of different class are altogether dissimilar When this idea has once been suggested we immediately that in three impor- tant, one may say vital, features, the stages of the life of a larger planet must differ markedly from those of Q small one.
 a planet will have shorter stages of life, smaller gravity, energy at it's surface, less water per square mile of surface, and even in more marked degree less air per square mile. Hence, since water and air are the denuding agents and gravity the force which works them in producing denudation, it follows that with weaker tools, weaker hand holding them, and less time in which to use them, the smaller planet will accom- plish far less denudation on it's own sur face than the larger. Applying this to the moon, which has but one-sixth the gravity of the earth, the moon would have had probably about one sixth of the supply of water and one-thirty- sixth the supply of air per square mile, while the stages of life would have but one-sixth the duration of the corresponding stages of tho earth's life, we see that probably the work of denuda- ton on the moon would be but about one- thousandth part of what has been done on
 
 Hence we can understand how it is that 1 on the moon the great craters and ray sys- ! tems extending many hundreds of miles from them remain, which doubtless once | existed on the surface of the earth, but have long since disappeared from it. On l the moon the processes of denudation were not sufficiently active, and they did not | last long enough to remove those great | vulcanian masses; on the earth there was sufficient power and ample time to remove all traces of such features, and we can in like manner understand why on the earth great mountain ranges form a much more striking feature than on the moon, for the materials of the older vulcanian features of 1 the earth have been used to make the great mountain masses. On the moon the older vulcanian masses have not been so l used; hence naturally there are but few l great mountain ranges, and these not com parable with the chief mountain masses of the earth.
 Thus finally we can study our moons 1 face, not only to tell us of the probable future of our earth as a dead world, but I also to tell us of the past, seeing on the 1 less worn face of our satellite the features 1 which have long since disappeared from the denuded surface of our earth.